The present invention relates to an improved exhaust gas recirculation (EGR) valve, and more particularly to an EGR valve including an electric actuator that converts rotary motion to linear motion.
Various systems have been developed to reduce the emission of undesirable combustion products, such as nitrogen oxides (NOX), from internal combustion engines. One such system is the EGR system. In EGR systems, a portion of the engine exhaust is recirculated into the intake manifold where it mixes with incoming air. The mixture of the exhaust gases with the air-fuel mixture in the engine cylinders provides lower peak temperatures during combustion, resulting in a reduction in the quantity of NOX produced.
Conventional EGR systems utilize an EGR valve to regulate the flow of exhaust gases from an internal combustion engine back into the intake manifold of the engine. The EGR valves in these conventional systems are known to be vacuum-operated (i.e., using intake manifold vacuum as a power supply for operating the valve) or electrically-operated (i.e., using an electric solenoid). EGR valves are also known that use an electric vacuum regulator (EVR) to control the supply of intake manifold vacuum to a conventional vacuum-operated EGR valve.
A disadvantage of known electrically operated EGR valves is that exhaust gas flow is related to the characteristics (speed, displacement, etc.) of the electric operator. However, it is desirable to control the exhaust gas flow without costly and complex electronics for customizing the characteristics of the electric operator.
The present invention provides a valve including a motor having a torque output shaft, a cam disposed on the torque output shaft, the cam having a profile, and a valve assembly including a valve and a pintle. The pintle is disposed in the valve and adapted to permit and prohibit delivery of exhaust gas from the valve. The pintle is also in contact with the profile of the cam such that constant rotary motion of the torque output shaft is converted to linear motion of the pintle having a variable acceleration.
The present invention further provides a valve including a motor having a torque output shaft, a cam disposed on the torque output shaft, and a valve assembly including a valve, a pintle, and a contact. The pintle is disposed in the valve and adapted to permit and prohibit delivery of exhaust gas from the valve. The contact is disposed at an end of the pintle and directly contacting the cam with the pintle. One of the cam and the contact has a profile such that constant rotary motion of the torque output shaft is converted to linear motion of the pintle having a variable acceleration.